Elevated B-type natriuretic peptide (BNP) has been shown to be strongly predictive of adverse outcome following myocardial infarction (MI). Chronic change in BNP after MI is less well studied and it is not known whether this adds any additional prognostic information
Method In 1995, individuals who had sustained an index myocardial infarction in the preceeding were invited to attend the Western Infirmary, Glasgow to undergo screening; this included blood sampling, medical history and echocardiography. BNP levels were also assessed. A second round of screening was subsequently performed in 1998. All deaths up to 31 December 2006 were collated from the General Register Office for Scotland.
Results Four hundred and eighty-one patients had BNP levels measured in both the 1995 and 1998 screening. Baseline median (IQR) BNP was 33.0 (51.8) pg/ml. Baseline BNP, was strongly predictive of outcome; the quartile with the highest BNP level had adjusted HR for all cause mortality of 3.15 (1.78–5.58) compared to the lowest quartile. Absolute change (Ä) in BNP between the screening visits was normally distributed with a mean change of +25.3±100.4 pg/ml, and ranged from −233 to+1151 pg/ml. There was no significant relationship between baseline BNP and subsequent Ä BNP; baseline log BNP did not correlate with Ä BNP (r=0.035, p=0.479). ÄBNP added no further prognostic information; the quartile with the highest change (mean change +114.2±162.9 pg/ml) was not predictive of outcome compared to the lowest quartile change (mean change −36.3±38.4) with an adjusted HR of 1.17 (0.68–2.00) for all cause mortality. Crude mortality was slightly higher in this group (30% vs 22%, p=ns), but not significantly so.
Conclusion BNP is a strong predictor of adverse outcome, even when assessed many years after MI. However, direct comparison of BNP measurements taken many years apart adds no further prognostic information, even if there are marked increases or decreases in levels.
- myocardial infarction
- B-type natriuretic peptide